If marciano, dempsey and louis had put on 100lbs of blubber could they have got become contenders?

There are still guys that tall who are around their weight

And Buddy was heavy

 

Fury was 260 pounds a few times.
A lot of the guys I mentioned were no where close to that and could not have functioned as well as Fury under old methods if they did.

 

Just because the tall men at heavyweight are all on average clearly heavier now (at least most of the relevant ones, besides Wilder), does not mean the lighter tall guys no longer exist.
They still exist.

Fury is 6'8-6'9, with an 85" reach.

Petiffer and Buddy Baer weren't as tall, nor as reachy.
While height and reach doesn't necessarily mean you're bigger, it's safe to assume that Fury is the clearly bigger man.

And those were the 2 biggest guys you listed.

And there are still guys who are tall and light.
I can find a lot of examples of them.

If you want I can give you a list of 10+ current middle and supermiddleweights who are 6'2-6'3. Most of them will be poop though.
They are lighter than pretty much all of those classic heavyweights around their height.

Kingsley Ikeke was a 6'4 career middleweight who has fought at 154.
There's Guillermo Jones, Cunningham.
Paul Williams

At SMW there are plenty of guys who are 6'2.

At lightheavyweight, there are a lot of 6'3 guys too.

But looking for 6'3 middleweights isn't that hard either, they generally are pretty bad though.


Carlos Negron is 6'6-6'7 and he has fought below 190 pounds 9 times.
He retired in 2013 but came back in 2015, I think a little fatter and weighted a bit heavier. (228, 223, 236)

And I'd say that Deontay Wilder is clearly a light guy.
6'7 but always below 230 pounds.

Donovan Dennis isn't very heavy either, although he's ****.

 

Buddy Baer weighed just as much as modern fighters his height throughout his career so wrong there yet again...

So why did some fighters post 1980 weigh just as much as the likes of Terrell at a similar height???

 

A lot of those "lighter guys" are playing the hydration game. Everyone knows nearly every fighter bellow heavyweight is in the wrong division. so what ever a guy's weight is 24 hours before is generally not within the weight class he would be on fight night if it was same day weigh in.

Supposedly Canilo Alverez is a cruiserweight on fight night.

In the heavyweight division the opposite is true. However much weight a guy can develop into and still function to his strengths is the order of the day. And this maximum is now beyond what was previously possible when among even heavyweights the order of the day was often training down to what ever condition produced the best boxing.